Thermionic converter



Nov. 4, 1969 R. L. LAING THERMIONIC CONVERTER 4 Sheets-Sheet 2 FiledAug. 9, 1967 FIE 5' INVENTOR. eoazer .L. 4 4/1116 Maw A r men/5V Nov. 4,1969 R. L. LAING 4 THERMIONIC CONVERTER Filed Aug. 9, 1967 '4Sheets-Sheet 5 INVENTOR. 165 805552 4. 44/06 F IE 11 ATTOPA/EI N v- 4.1969 R. L. LAING 3,477,012

THERMIONIC CONVERTER Filed Aug. 9, 1967 4 Sheets-Sheet 4 J40 i 14Z FIE 8J55 J52 II 155 INVENTOR.

EOEEEZ AAA/Iva BY X United States Patent O US. Cl. 322-2 21 ClaimsABSTRACT OF THE DISCLOSURE A thermionic converter in which a source ofheat is used to apply heat to a cylindrical cathode which is surroundedby a cylindrical anode for accelerating the passage of the electronsfrom the cathode to at least one collector disposed adjacent an end ofthe anode and in which there is magnetic means surrounding the anode andproducing a magnetic shield generally parallel to the axis'of the anodefor confining the electrons emitted by the cathode and minimizing thetendency of said electrons to engage said anode in passing from thecathode to the collector, there being a utilization circuit connectedbetween the collector and the cathode to draw the energy from thecollector, this utilization circuit being free of any externalelectrical source of power of the same order of magnitude of energy asthat of the source of heat for heating the cathode.

BACKGROUND OF THE INVENTION The present invention is concerned with athree-element type of thermionic converter in which there is a cathodefor emitting electrons, an anode for accelerating the electrons, and acollector to which the electrons go after passing the anode. In such adevice, there is a utilization circuit connected between the collectorand the cathode and the load device is connected in this utilizationcircuit. The thermal energy to be converted into electrical energy isapplied to the cathode to cause electrons to be emitted therefrom andthe primary function of the source of power connected to the anode is toapply a potential such as to cause the electrons to be accelerated.Desirably, no appreciable current flow is in the anode circuit so thatthe source of power connected to the anode does not substantiallycontribute to the power input to the converter.

In the Laing and Feemster Patent 3,275,923, in which the presentapplicant is a co-inventor, use is made of a relatively fieldless hollowcollector. As is pointed out in this patent, the hollow collector hasthe advantage that once the electrons leave the anode and enter thehollow collector, they are repelled away from each other to engage thewalls of the collector. Thus, any tendency for a virtual cathode to beformed by reason of the space charge from slow-moving electrons in frontof the collector surface is very substantially reduced or eliminated. Inthis prior patent, however, the electron beam is confined to a directline extending from the cathode so that the cathode emission is reducedby the space charge depressed field of the beam.

In the Hatsopoulos Patent 2,915,652, there is disclosed a three-elementthermionic converter in which a cross field is used to deflect theelectrons leaving the cathode and to cause them to be directed towards acollector plate which is either flat or in some cases, convex. Anarrangement of this type has the drawback that a virtual cathode isformed adjacent the collector surface by reason of the space charge fromslow-moving electrons, as previously mentioned. This tends to retard thepassage of electrons from the cathode to the collector.

SUMMARY OF THE INVENTION The present invention is concerned with athermionic converter having a portion similar to a magnetron in-3,477,012 Patented Nov. 4, 1969 lCC jection gun for providing anelectron stream. This means for providing an electron stream includes anaccelerating means for accelerating the charged particles, whichaccelerating means has an elongated curved surface spaced from and atleast partially surrounding a cylindrical surface for emitting chargedparticles, and a magnetic means surrounding the accelerating means andproducing a magnetic field generally parallel to the longitudinal axisof the curved surface of the accelerating means for confining thecharged particles emitted by the emitting surface and minimizing thetendency of the charged particles to engage the accelerating means.While I have shown a cathode as the means for emitting the chargedparticles, the

shown the accelerating means as an anode having a positive voltageapplied thereto, the invention contemplates the possibility of a similararrangement using ions or other charged particles instead of electrons.Where the particles are charged positively, the polarities of thevarious voltages applied to the various electrodes will be opposite tothose employed with electrons.

In one broad form of my invention, the anode is a cylindrical membercompletely surrounding the cathode and the collector is adjacent one endof the cathode. In fact, there may be a pair of collectors employed, oneadjacent each end of the anode. In another broad form of my invention,the anode extends only partially around the cathode and the collectorsurrounds the cathode and anode so that the charged particles orelectrons move past the anode and engage the surrounding cylindricalsurface constituting the collector surface.

In some instances, 1 may employ a hollow collector having an openingfacing the region between the cathode and anode. There may also beemployed an additional collector in the form of a flat plate. Inaddition, the collector may be disposed intermediate the opposite endsof the anode, and may take the form of a helical coil. Instead of a flatplate, it is possible to employ two hollow collectors each having anopening facing the region between the cathode and anode. It is alsopossible to have the magnetic field diverge in the direction of theopening in the collector to facilitate entry of the electrons into thecollector. The means for heating the cathode may take various forms. Insome instances, this may take the form of a flame designed to heat theinterior of the electron emissive surface. Or the cathode may enclose orbe composed of radioactive material. In other instances, the cathode maybe tubular and the source of heat may be a source of heated fluid whichis circulated through the cylindrical cathode. It is also possible toemploy a reflector adapted to be exposed to solar energy and in whichthe cathode is adjacent the focal point of the reflector.

The anode may take various forms. For example, it .is possible to employaxial barlike electrodes which extend axially inside of the anode andare maintained at a different potential than the anode. It is alsopossible to employ an additional electrode, disposed between the anodeand collector and which is maintained. at a potential such as tomaximize the amount of energy withdrawn from the converter.

In the direct beam device of the Laing and Feemster Patent 3,275,923,the forces necessary to drive the electrons onto the negative collectorare derived from the combination of mutual repulsion due to space chargein an essentially fieldless negative collector plus the velocity causedby cathode heat. In the Hatsopoulos Patent 2,915,- 652, the forcesnecessary to drive the electrons onto the flat or convex collector arederived primarily from the heat energy of electrons leaving the cathode.In the present invention, the forces that cause electrons to be drivenonto the negative collector are derived not only from the mutualrepulsion of space charge and a concave relatively fieldless collector,plus the velocity imparted to the electrons due to cathode heat, but inaddition to this, considerable extra velocity is imparted to theelectrons towards the axial ends of the magnetron injection gun orcompression chamber due to the magnetic fields which are establishedboth in axially spinning electrons called Bohr magnetrons, and also inelectrons spinning in a magnetron orbit. Additional forces are built updue to accumulation of space charge in the magnetron compressionchamber, all of which enhances the velocity of the electrons towards thenegative collector. These effects are further increased by the fact thatthe charged particles are forced out of the chamber at areas ofirregularities or openings in either the electrostatic field orelectromagnetic field, or a combination of both, due to the generationof space charge waves at such areas so that the charged particles leavethe compression chamber with greater individual kinetic energy than theaverage kinetic energy of the charged particles within the compressionchamber. Because of this additional energy, the charged particles can becollected on a highly charged collector electrode.

Therefore, while a converter of the type shown in the Hatsopoulos patentis able to produce output voltages of less than minus one volt, thepresent invention enables voltages of 200 volts at the maximum outputefliciency, and open circuit voltages up to 900 volts, in actualexperiments.

In addition to the possible modifications of my invention describedabove, various other modifications and various other objects of theinvention will be apparent from the accompanying specification anddrawing.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a vertical sectional viewof one form of my thermionic converter with a flame being shown as themeans for heating the electron emissive surface;

FIGURE 2 is a fragmentary view showing a modification;

FIGURE 3 is a vertical sectional view of a further form of my inventionemploying a. magnetic member adjacent the collector aperture and showingradioactive material as the source of heat, and also showing anadditional collector in the form of a disc disposed intermediate theopposite ends of the anode;

FIGURE 4 is a vertical sectional view of a further form of my inventionemploying a substantially spherical collector at one end of the anodeand showing a perma nent magnet for producing a magnetic field whichdiverges outwardly adjacent the opening to this collector;

FIGURE 5 is a' vertical sectional view of a still further form of myinvention in which the cathode is in the form of a tube through whichhot fluid is circulated and in which there is an intermediate helicallywound coil concentric with the cathode and anode and disposed betweenthe two;

FIGURE 6 is a vertical sectional view of a further species of myinvention in which the anode is provided with axial bars which areelectrically insulated from the anode and which are maintained at alower potential than the anode proper;

FIGURE 7 is a cross-sectional view of the thermionic converter of FIGURE6, the section being taken along a plane defined by the line 7-7 ofFIGURE 6;

FIGURE 8 shows a species in which certain of the electrodes arecontoured to maximize the collection of electrons on the collectorsurface. In addition, in FIG- URE 8, I have shown a parabolic reflectordesigned to reflect the solar energy into the interior of the electronemitting cathode;

FIGURE 9 is a further form in which the anode is only partiallycylindrical and in which the electrons are deflected past the anode ontothe interior of a cylindrical collector;

FIGURE 10 is a cross-sectional view taken along the line ltll0 of FIGURE9; and

FIGURE 11 shows a modification of the species of FIGURES 9 and 10 inwhich an additional electrode has been inserted, which electrode iscurved to conform with a potential plane existing within the collectorand which is maintained at an intermediate potential such as to maximizethe passage of electrons to the collector surface.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGURE 1, mythermionic converter is shown as comprising a cylindrical hollow cathode11 which is closed at its upper end and is open at its lower end. Thecathode may either be formed of an electron emissive material, such asthoriated tungsten, or may be coated on its exterior surface with asuitable electron emissive material. The lower end of the cathode ishermetically sealed at 12 to a circular base member 13 of heat resistantinsulating material, such as ceramic. A cylindrical collector 14 has aclosed upper end 15 and a lower open end which closely fits over thebase member 13 and is suitably hermetically sealed thereto. Thecollector 14 may either be of highly conductive material or may beformed of less conductive material with an interior conductive coating.

Also secured to the base member 13 in any suitable manner is acylindrical anode member 17 which is mounted within the assembly withthe axis thereof parallel to the axis of the cathode 11 and thecollector 14. An auxiliary collector 18 in the form of an apertured discsurrounds the cathode 11 and is secured to the upper surface of theinsulating base member 13 coaxially of cathode '11.

In some instances, it is desirable to employ a probe 19 which is shownas being electrically connected at 20 to the collector 15. As will beexplained in more detail, the probe 19 acts as the pickup probe to aidin the collection of the electrons by the collector 14 or acts as toshift the electric field lines in such a way as to maximize thecollection of electrons by the collector.

The entire equipment described so far is hermetically sealed togetherand evacuated. The techniques of such evacuation and sealing are wellknown and are not described in detail herein.

Surrounding the unit adjacent the anode 17 is a cylindrical permanentmagnet 22 which cylindrical magnet is coaxial with the anode 17 andproduces a magnetic field generally parallel to the surface of the anode17.

Various means may be employed for heating the cathode 11. Since thedevice is intended to function as a thermionic converter, the source ofheat may be any suitable source of heat which it is desired to convertinto electricity. In the particular embodiment in FIGURE 1, I have showna conventional burner 23 in which the lilime therefrom extends into theinterior of the cathode The anode 17 is maintained at a positivepotential with respect to cathode 11 by any suitable source of voltageshown for illustrative purposes as a battery 25, the positive terminalof which is connected by conductor 26 to the anode 17 and the lowerterminal of which is connected to ground at 27, this connected to thecathode 11 through conductor 28.

In the operation of my device, as will be presently described, the heatto be converted to electricity is used to heat the cathode and theelectrons emitted therefrom are caused to move to the interior surfaceof the collector 14 and onto the auxiliary collector 18. Because of theelectrons being negative, the collectors 14 and 18 become highlynegative.

A suitable load device 30 has one terminal thereof connected byconductors 31 and,32 to the collector 14 and has the opposite terminalthereof connected to ground by conductor 33. The load 30 is thusconnected between the collector 14 and ground so that the electronsaccumulating on collector 14 can flow thro gh the load device 30 groundconnection 27 being,

back to the cathode 11. The load device 30 is similarly connectedthrough conductors 28, 33, 31, and 34 between the cathode and theauxiliary. collector 18 so that the electrons accumulating on auxiliarycollector 18 can flow through conductors 34 and 31, the load device 30and conductors 33 and 28 back to the cathode 11. In some cases, it maybe desirable to employ a separate load device between the auxiliarycollector 18 and the cathode since the, negative potential which theauxiliary collector 18 assumes may be different than that assumed by thecollector 14.

Referring to the operation of FIGURE 1, the electrons emitted from thecylindrical surface 11 are attracted to the annular anode 17. They areprevented, however, from actually engaging the anode 17, to anyappreciable extent, by the magnetic field produced by magnet 22, thelines of force of which run parallel to the anode 17 between the anode17 and cathode 11. The beam of electrons is thus deflected and tends totravel in the space between the cathode 11 and anode 17. The effect ofthe magnetic field tends to cause the electrons to rotate so that theytend to travel in a helical path between the cathode 11 and the anode17. As the electrons spin in magnetron orbits in the chamber between theanode 17 and the cathode 11, they are repelled out of that region bytheir own mutual repulsion, and also are magnetically attracted to thepoles of the magnet, which are adjacent to the collector, due to bothelectron axial and magnetron spin velocities. As they approach the upperend of anode 17, they are also repelled by the lower electrons into thehollow space formed by collector 14. Once they enter this hollowcollector, they are in a relatively field-free region and are repelledby each other to engage the interior wall of the collector much aselectrons go to the outside of a hollow Van de Graaif generatorcollector. The electrons which pass downwardly engage the auxiliarycollector 18. Both the electrons engaging the wall of the hollowcollector 14 and those engaging the flat auxiliary collector 18 flowthrough the load 30 back to the cathode.

The pickup probe 19, where used, tends to aid the electrons in passingto the wall of the hollow collector since this probe is locatedcentrally of the hollow collector and is engaged by those electronsfurthest from the wall of the collector. Furthermore, as pointed outabove, the probe acts to shift the electric field lines to maximize thecollection of electrons by the collector. The latter effect can beobtained even if the probe is insulated from the collector and thepotential thereof adjusted for maximum collection.

With the arrangement just described, it is possible to obtain very highvoltages as compared with a conventional thermionic converter. Aspointed out above, instead of a voltage output of less than a volt, Ihave obtained voltages of approximately 200 volts between the collectorand the cathode while drawing maximum power through the load. Byemploying the magnetic field 22 to prevent the electrons engaging theanode 17 and by giving the electrons a spiraling effect, it is possiblefor a much larger propor tion of the electrons leaving the cathode 11 tobe forced onto the collector surface with only 'a relatively smallportion of the electrons engaging the anode surface, As has been pointedout, the ideal situation is to have the anode 17 act merely as a meansfor attracting the electrons without any of the electrons ever touchingthe anode. Under ideal conditions, the current flowing in the anodecircuit should be substantially negligible.

The arrangement of FIGURE 1 in which the flat collector 18 is directlyconnected by conductors 34 and 32 to the hollow collector 14 tends tocreate. an oscillatory condition due to transient eflects causingimaging currents at collectors 14 and 18, which are fed from eachcollector back to the other. In one particular instance, a frequencycomponent of 50 mHz. was found to exist. This further aids in thecollection of the electrons.

6 In FIGURE 2, I have shown a modified form of pickup probe. In thiscase, the probe instead of being in the form of a longitudinal wire-likeelectrode, as in FIGURE 1, is in the form of a circular ring 36 which isconnected at 20 to the collector 14, This ring has the advantage ofhaving a somewhat extended surface which is engaged by more of theelectrons entering the collector chamber.

FIGURE 3 shows a further modification of my invention. In this case, thehollow collector 44 is of substantially the same configuration ascollector 14 of the species of FIGURE 1. Instead, however, of employinga flat insulating disc, I employ a cup-shaped insulator member 43 whichis provided at its upper end with an inturned flange 45. The cathode 41,as with cathode 11, is hollow and has an open lower end. Since I haveshown radioactive material 46 as the source of heat in thismodification, I have shown the lower end of the cathode as being closedby the insulating member 43 so that the interior of the cathode issealed from the atmosphere. It is to be understood that even though thecathode 41 is entirely within the enclosure formed by insulating member43 and collector 44, it is desirable to have the lower end of thecathode 41 sealed to the upper surface of insulating member 43 toprevent the escape of radioactive material into the area surrounding thecathode. The anode 47 in this modification is in the form of an annularsleeve which engages the interior of the upstanding cylindrical wall ofthe cupshaped insulating member 43, this cylindrical wall serving toelectrically insulate the anode 47 from the collector 44.

In the modification of FIGURE 3, there is a cylindrical magnetic polepiece 48 which is secured on top of the flange 45 of the insulatingmember 43 and which is formed of magnetic material. This magnetic membertends to aid the entry of the electrons into the hollow collector 14 inseveral ways. In the first place, the line of force of the magneticfield do not extend beyond the magnetic member 48 because of the factthat this magnetic member forms an easier means of passage of themagnetic lines of force into the area between the anode and cathode.Furthermore, the magnetic field extends more closely adjacent to theanode by reason of being directed by the downwardly turned fiange ofmagnetic member 48. The magnetic field thus has less effect on theemission from the cathode. To aid this effect, I also provide a lowermagnetic cylindrical sleeve 49 which is of the same diameter as thedownwardly turned flange of magnetic member 48. This tends to shortenthe air gap in the magnetic field causing it to pass more closelyadjacent to the interior of the anode 49. Located adjacent to thecylindrical magnetic sleeve 49 is an auxiliary collector 51 which has anupturned cylindrical portion 52. This auxiliary collector member 51,like collector member 44, is of conductive material. A further advantageof the magnetic members 48 and 49 is that these tend to attract theelectrons to the collector since each electron tends to act like a tinymagnet due to both axial spin and magnetron orbital spin. Thus, themagnetic members 48 and 49 not only serve to limit the extent of themagnetic field and decrease its tendency to enter the hollow collector44 but they also serve to confine the magnetic lines of force moreclosely to an area adjacent to the anode 47 and further to aid theelectrons in being magnetically attracted into the collector areas.

' A further feature of the modification of FIGURE 3 is that I provide anauxiliary intermediate collector 53. This auxiliary collector 53 is inthe form of a fiat annular disc having a central aperture therethrough,the disc being suitably mounted by a suitable means, not shown,concentrically with the cathode 31 with the cathode extending throughand spaced from the walls of the apertured disc in the collector 53.

' As with the species of FIGURE 1, a positive voltage is maintainedbetween the anode 47 and the cathode 41 by a suitable source of voltagesuch as battery 55, the positive terminal of which is connected byconductor 56 to the anode 47 and the negative terminal of which isconnected by conductor 57 to ground connection 58 to which the cathodeis connected. In the present embodiment, I employ three loads 59, 60 and61. The load 60 corresponds to load 30 of FIGURE 1, being connectedbetween the main collector 44 and the cathode. The load 59 is connectedbetween the magnetic member 49 associated with collector 51, and thecathode. The load 61 is connected between the intermediate collector 53and the cathode. By using three separate loads, it is possible for eachof the collectors to be maintained at a different potential and toobtain the maximum efiiciency in collection of the electrons on therespective collector surfaces.

The intermediate collector 53 has the advantage that there is sometendency for a portion of the electrons to be attracted to the center ofthe magnetic compression chamber and by placing the collector 53 in anintermediate portion of this chamber, such electrons are collected bycollector 53 and caused to flow through load 61.

The modification of FIGURE 4, like the modification previouslydescribed, employs a hollow cylindrical cathode 64 which extends throughan aperture in an insulating disc 65 which may be of ceramic material.The cathode 64 is hermetically sealed to the disc 65 and the interior ofthe cathode is heated by a suitable source of heat such as a burner 66,the flame of which extends into the interior of cathode 64. Acylindrical anode 67 is sealed at its lower end to the insulating disc65, this anode being mounted concentrically with respect to the cathode64. Secured to the upper end of the anode 67 is a spherical conductivecollector member 68 which has an opening 69 therein adjacent theinterior of the anode member 67. A ceramic spacer sleeve 70 isinterposed between the collector 68 and the upper end of the anodemember 67, being hermetically sealed to both the anode and the collector.

In the modification of FIGURE 4, I have provided for a divergentmagnetic field. To accomplish this, I provide an annular magnetic member71 shown as a permanent magnet. This magnetic member is provided withupper and lower annular openings 72 and 73 to provide opposite poleportions. The lower magnetic opening 73 is disposed adjacent the lowerend of anode member 67 and the upper opening 72 surrounds the lowerportion of the spherical collector 68. It will be noted that the upperopening 72 is substantially larger than the lower opening 73. In orderto guide the magnetic lines of force, I have .provided a cylindricalmagnetic member 75 which converges upwardly and which is ofsubstantially the same diameter as the opening 73 at the lower end ofthe magnet. The upper portion of magnetic member 75 converges so thatthe interior of the upper end of this member more closely approaches theexterior of the cathode member 64. It will be readily apparent from thelines of force indicated by reference numerals 76 and 77 that themagnetic field is initially confined by the magnetic member 75 to apoint closely adjacent to the cathode 64. As it passes upwardly to theupper portiton of magnet 71, it diverges. The effect of this is topermit the electrons to diverge as they pass upwardly. By confining theelectrons at the lower end of the chamber and permitting them to divergeas they pass upwardly, the tendency for the electrons to engage theanode 67 is minimized and the tendency of the electrons to enter theinterior of the hollow chamber 68 is increased. Once they enter thehollow collector chamber 68, they are in a relatively field-free regionand the mutual repulsion of the electrons causes them to spread out andengage the interior of the collector.

As with the other modifications, a load device 80 is connected betweenthe collector 68 and the cathode 64 through connections which arereadily apparent from the drawing. Similarly, as with the othermodifications, the anode 67 is maintained at a suitable positivepotential with respect to the cathode by a suitable source of tial, suchas battery 81.

In the species of FIGURE 5, the cathode 82 is in the form of acylindrical tube through which hot fluid is circulated. The hot fluid isthe source of heat energy which is to be converted into electricalenergy. It is to be understood that the' portion of the tube 82extending through the converter is coated with a suitable electronemissive material.- The anode 83 is in the form of a cylindrical sleevewhich is sealed at its end to annular insulating members 84 and 85 ofheat resistant insulating material, such as ceramic. Sealed to theinterior of these annular insulating members 84 and 85, respectively,are cylindrical members 86 and 87 which are formed of magnetic material.and constitute part of the collector structure. Further annularinsulating members 88 and 89 are sealed to the collector members 86 and87 and to the cathode tube 82. Extending between the two magneticcollector members 86 and 87 and electrically connected thereto is ahelically wound wire 91 of electrically conductive material. The helicalturns of the coil 91 are preferably wound in the same direction as thedirection of rotation of the magnetic beam, this direction of rotationbeing determined by the polarity of the magnetic field. Where the coilis wound in the same direction as the direction of magnetic field, thecurrent flowing through the coil between the two magnetic collectormembers 86 and 87 tends to attract the moving electrons just as twowiresconducting current in the same direction are attracted to oneanother. For relatively small currents, it may be desirable to have thehelical coil 91 wound in the opposite "direction to the direction ofrotation of the magnetic field so that there is more tendency for theelectrons to engage the turns of the wire 91. Or the helical wire 91 maybe wound in opposite directions in each axial direction beginning at thecenter of the coil.

'Itis, of course, to be understood, as with the other species, that theinterior of the chamber enclosed by anode 83 is highly evacuated in amanner commonly employed in electronic discharge devices.

Surrounding the sealed unit enclosed by the anode 83 is a cylindricalpermanent magnet 93 having inturned opposite ends which are apertured toprovide opposite poles. The cathode 82 extends through the apertures inthe magnet 93. The magnet 93 produces a magnetic field which extendsgenerally to the anode 83 within the same.

Still referring to the species of FIGURE 5, a suitable source ofpotential such as the battery 94 is connected between the anode 83 andthe cathode'82 so as to apply a positive potential to the anode 83. Asuitable load device 96 is connected between the magnetic collectormember 87 and the cathode 82 so as to be connected between the collectorassembly and the cathode.

In the arrangement of FIGURE 5, the electrons leaving the cathode areattracted to the anode 83 but are prevented from engaging the anode 83to any substantial extent by the magnetic field created by magnet 93.The electrons are thus forced to travel spirally in opposite directions.Some of these electrons are collected by the helical wire 91 and someenter the magnetic collectors 86 and 87, being attracted thereto by themagnetic action between the collector members and the spinningelectrons. The electrons fiow through the load device 96 back to thecathode.

Referring to the species of FIGURE 6, the cathode is indicated by thereference numeral 99. This cathode is either formed of electron emissivematerial or coated with an electron emissive coating. The cathode takesthe form of an inverted hollow tube as in the other species. Extendinginto this tube is a burner 100 which is of a type which burns a mixtureof gas and air or oxygen and acetylene, etc. A gas supply line 101supplies gas to the burner and an air supply line 102 supplies airthereto. The gas and air are passed through passages 103 and 104,respectively,

potenand pass out through the burner 100 where they are mixed andburned. As with some of the other modifications, the anode 105 takes theform of a cylindrical sleeve of conductive material. This sleeve issecured at its opposite ends to annular members 106 and 107 of suitableheat resistant insulating material, being hermetically sealed thereto.Hermetically sealed to the inner wall of the annular insulating disc 106is a cup-shaped collector member 110, likewise formed of conductivematerial. Secured to the interior surface of the annular insulatingmember 107 is a flat collector plate 111 of conductive material. Thisflat collector plate, along with the rest of the assemblage, issupported from the cathode 99 by an interposed annular insulating member112 which is hermetically sealed to the collector plate 111 and to thecathode 99.

In this modification, I provide a plurality of auxiliary anodes 114 inthe form of longitudinal bars or cogs of conductive material. As bestshown in FIGURE 7, which is a cross-sectional view taken along the line77 of FIGURE 6, these bars 114. are uniformly spaced about the peripheryof the cathode 99 being suitably spaced therefrom. Each of the bars 114is insulated from the main anode 105 by a series of insulating posts115.

The entire assemblage including the collector members and the anodemember with the enclosed cathode and auxiliary anode members 114 ishermetically sealed and evacuated. Surrounding this evacuated structureis an electromagnetic winding 117 which produces a magnetic fieldsimilar to that of the other species, this magnetic field passingbetween the anode and cathode and generally parallel thereto. Anysuitable energizing means, not shown, is employed for energizing thewinding 117.

In this species, as shown, I maintain the main anode 105 at a higherpotential than the auxiliary bar electrodes 114. A first source ofpower, such as a battery 118 is connected between the cathode and theauxiliary anodes 114. While I have shown the connection to only one ofthese anodes, it is to be understood that a similar electricalconnection is made between battery 118 and the other auxiliary anodes. Asecond source of power such as a battery 119 is interposed between theauxiliary anodes and the main anode 105 so that the main anode 105 ismaintained at a higher potential than the auxiliary anodes. While I haveshown the auxiliary anodes as being maintained at a lower potential thanthe main anode 105, in some instances, it may be desirable to have theauxiliary anodes at the higher potential, relying upon the spacingbetween the auxiliary anodes to prevent the electrons from engaging theauxiliary anode. The effect of the auxiliary anodes connected as shownin the drawing, however, is to minimize any tendency of the electrons topass to the high potential anode 105. This, of course, is aided by theeffect of the electromagnetic field.

While I have shown longitudinally extending bars 114 as constituting theauxiliary anode, it is to be understood that these auxiliary anodes oranode may take any other form. For example, it is possible to employ,instead of bars, a coiled wire such as wire 91 of FIGURE 5. In such acase, the coiled wire, instead of acting as auxiliary collector as inFIGURE 5, would act as an auxiliary anode, being maintained at adifferent potential than the main anode.

It is also possible to have the longitudinally extending bars connectedto the opposite collector members and act as part of the collectorstructure, instead of being connected to a source of voltage to act asauxiliary anodes. These bars in such an arrangement would function in amanner similar to the coiled wire 91 of FIGURE 5. In such a case, thebars may be concave to increase the collecting effect.

It is also possible for the bars 114 or a coiled wire such as wire 91 tobe connected to a variable negative source of voltage to function as agrid. In such a case, this auxiliary electrode or electrodes would beinsulated from the anode and collector as is the case with the bars 114.

In the modification of FIGURE 8, I have shown an arrangement in whichsolar energy is employed to heat the cathode. Furthermore, I have shownan arrangement in which certain of the electrodes are curved to moreeffectively direct the electrons onto the collector surface. Referringspecifically to FIGURE 8, the thermal converter is supported from aparabolic mirror by a plurality of struts 126 which engage an invertedcupshaped collector 127 of suitable conductive material. The cathode 128is cylindrical and hollow with the hollow portion facing downwardly, asin other modifications. Secured to the cathode 128 is a conical flange129 of conductive material which is hermetically sealed at its outerupper edge to an annular ring 130 of suitable heat resistant insulatingmaterial such as a ceramic. The anode 131 is basically cylindrical butcurves inwardly so that its diameter at its upper end is substantiallyless than its diameter at its lower end. This lower outer edge of theanode 131 is hermetically sealed to the insulating member 130 and to asecond similar annular insulating member 133 which, in turn, ishermetically sealed to the lower end of the collector 127. Thus, thecathode, the anode and the collector are held together to form ahermetically sealed enclosure which is suitably evacuated.

The cathode 128, in this embodiment, is provided with an elongatedinverted conical electrode 135 which electrode is of conductive materialand functions as a focusing electrode. Because the electrode isconnected to the cathode, it is at the same ground potential as thecathode. In this embodiment, I have also shown a curved shield 137 whichis either integral with or conductively secured to the lower end of thecollector 127 and extends upwardly and inwardly from this lower end. Thegeneral curvature of this shield corresponds approximately to thecurvature of the anode 131. The shield 137 functions as a Faraday shieldto tend to reduce the effect of the electrons to go to the anode 131.

To further aid the direction of the electrons, I provide a beamcontrolling sole 139. A conductor 140 connected thereto through aninsulator 141 located in the upper wall of collector 127 extends to asuitable source of positive voltage such as a battery 142. The battery142 tends to maintain the sole at a slightly positive potential withrespect to the cathode, this positive potential being relatively small,however, as compared with the voltage applied to the anode 131.

Permanent magnet 141 extends around the outside of the collector 127 andserves to provide an axial field which passes between the anode 131 andthe cathode 128 including the focusing electrode 135.

As with the other forms of the invention, the anode 131 is maintained ata positive potential with respect to the cathode 128 by a suitablesource of power such as a battery 143. Similarly, a suitable load 144 isconnected between the collector 127 and the cathode 128 so that theelectrons reaching the collector flow through this load resistor back tothe cathode.

The parabolic mirror 125 is designed so that the rays of sun indicatedby the reference numerals 146 are reflected into the interior of cathode128. It other words, the cathode 128 is located at the focal point ofthe parabolic mirror 125. Because of this arrangement, the cathode 128can be intensely heated by the solar energy directed onto the reflectingsurface of mirror 125. It is to be understood, of course, that thearrangement involving the parabolic mirror 125 may be used with otherforms of the invention and that as far as the modification of FIGURE 8is concerned, other forms of heating the cathode may be employed.

Referring generally to the operation of the thermionic converter ofFIGURE 8, electrons leaving the surface of cathode 128 are directed asindicated by dotted lines 148 upwardly between the anode 131 and thefocusing elec- 1 1 trode 135. They are prevented from engaging the anode131 by the combined effects of the electromagnetic field and the Faradayshield 137. After passing upwardly beyond the end of the anode 131, theyare immediately repelled from each other so as to engage the interiorwall of the collector 127. This action is aided by the beam directingsole which exerts an attractive force upon the electrodes to furtheraccelerate the same. At the same time, because of its relatively lowpositive potential and because of the fact that the electrons by thetime they reach the region of the sole have obtained sutficient velocityin paths away from the sole, relatively few of the electrons engage thesole, substantially all of them passing beyond the sole and engaging theinterior walls of the collector from whence they are drawn away throughthe load 144. With this type of arrangement, in which the various beamguiding surfaces are curved, the electrons are very effectively directedtowards the interior collector surface with relatively little loss tothe anode or other auxiliary electrodes.

The arrangement of FIGURES 9 and 10 operates in a somewhat differentmanner in that the electrons instead of passing out beyond the end ofthe cathode are directed outwardly from the cathode in a curved path toengage a collector surface which is generally coextensive longitudinallywith the cathode. In this modification, as will be presently explained,the anode does not encircle the cathode but merely extends part wayaround it permitting the electrons to pass beyond the edge of the anodeand engage the collector.

Referring specifically to the structure shown in FIG- URES 9 and 10, thecathode is indicated by the reference numeral 150. This cathode, likethat of the other modifications is preferably of tubular form having thelower end thereof open. This lower end extends through and is sealed toa ceramic base plate 151. A suitable means, not shown, may be employedfor introducing heat into the interior of the cathode 150 to cause thesame to emit electrons. Also secured to the insulating base plate 151 isan inverted cup-shaped collector 152, the lower open end of which ishermetically sealed to the insulating base plate 151. The enclosureformed by the collector 152 and the base plate 151 is evacuated as inthe other species. Also secured to the base plate is an anode member 151which, unlike the other species, is only semi-cylindrical, as best shownin FIGURE 10. A sole electrode 154 is also secured to the insulatingbase plate 151. This sole, as shown in FIGURE 9, is of substantially thesame vertical extent as the anode 153 and the cathode 150. As best shownin FIGURE 10, the sole 154 has a curved portion 155 which is curved soas to be concentric with the cathode 150, the radius of curvature beingsomewhat larger than that of cathode 150 so as to be spaced therefrom.The intermediate portion of the sole 154 is in the form of a flat plate156. The outer portion of the ,sole' is bent at an angle to portion 156and closely approaches but is spaced from the collector 152. Thecollector is surrounded by a permanent magnet 158 having a magneticfield parallel to the cathode 150.

The anode 153, as in the other species, is maintained at a relativelyhigh positive potential with respect to the cathode by a suitable sourceof potential such as a battery 160. A load device 161 is connectedbetween the collector 152 and ground and hence between the collector andthe cathode. Another load device 162 is connected between the sole 154and the cathode.

In operation, the electrons leaving the cathode 150 tend to approach theanode 153 being attracted thereby. The magnetic field, however, producedby the magnet 158 is effective as indicated by the dotted lines 164 todeflect the electrons away from the anode 153 causing them to passoutwardly from beyond the right-hand edge of the anode 153 to engage theinner surface of collector 152. Due to the rotative effect of themagnetic field and the slowing down of the electrons as they approachthe negative and an acceleration of the electrons as they move backtowards the accelerating anode, the electrons will follow a trochoidalpath as indicated by the dotted lines. The electrons so engaging thecollector cause the collector to assume a relatively high negativevoltage and these electrons are conducted through the load 161 back tothe cathode. Any electrons which continue to curve around in a clockwisedirection, if they travel far enough, due to the mutual repulsionbetween the electrons, will engage the sole 154. These electrons will bepicked up by the sole and will travel back through load resistor 162 tothe cathode. The sole 154, by reason of the stray electrons engaging thesame, tends to assume a somewhat negative voltage, the magnitude ofwhich is determined by the magnitude of load resistor 162. The sole 154,being maintained at this negative voltage, prevents any electrons fromreturning to the cathode 150. It also protects against any electronscontinuing to move in a clockwise direction until they engage thepositively charged anode 153. The electrons traveling in this clockwisedirection are thus either forced onto the sole 154 or onto the collector152. In either case, the energy resulting from the movement of theseelectrons is utilized in either of the loads 161 or 162.

The arrangements of FIGURES 9 and 10, by reason of the concave collector152, the provision of the sole and the general organization of the unit,result in relatively high output voltages as compared with conventionalcrossed-field thermionic converters. I have obtained in one embodiment,a voltage output of l00 volts, such voltage being very much higher thanthose obtained with conventional thermionic converters. As with my otherembodiments, the magnetic field acts to compress the space chargecausing it to assume the nature of a compression chamber and due, inpart to areas of irregularities or openings in either the electrostaticfield or electromagnetic field or a combination of both, the chargesleaving the compression chamber have much greater individual kineticenergy than the average kinetic energy of the charges within thecompression chamber. Because of this additional energy, the electronscan be collecteo on the highly charged collector electrode 152.

While I have shown the base member 151 as being of insulating material,it is also possible for this to be of conductive material and eitherintegral with or electrically connected to the collector member 152. Insuch a case, it is, of course, to be understood that the cathode 150,the anode 153 and the sole 154 will be suitably insulated fro-m thislower member. The advantage of picking the lower member of conductivematerial is that any electrons which spiral out above or below the anode153 will engage a conductive surface of the collector and will increasethe current flowing through the load 161.

The species of FIGURE 11 shows an additional feature shown in connectionwith a thermionic converter of the type shown in FIGURES 9 and .10 butwhich can be employed with the other species. In order to enable a readycomparison of FIGURES 9 and 10 with FIGURE 11, the same referencecharacters have been used in connection with FIGURES 9 and 10, as far asidentical elements are concerned. Thus, there is a cathode 150,semicylindrical anode 153, a cylindrical collector 152 and a soleelectrode 154. In addition to the elements included in the species ofFIGURES 9 and 10, I have a further electrode 170 which is curved toconform to an equipotential surface within the chamber formed bycollector 152. This further curved electrode 170 will be ofsubstantially the same height as the anode 153 and is connected throughan adjustable load to the cathode 150. Because the auxiliary electrodelies in the path of electrons, it will tend to assume a negative chargeby reason of the electrons engaging this element. By adjusting the load165, the amount of this negative voltage can be adjusted. It ispreferable to adjust the negative voltage so that the voltage isslightly less negative than would otherwise exist along theequi-potential surface 13' existing at the location of this electrode170. It has been found in actual experiments that by doing so, theelectrons tend to travel deeper into the collector region and then to bedeflected through the area between the righthand end of the electrodeand the right hand end of anode 153, as shown by the dotted lines 175.As with the arrangement of FIGURES 9 and 10, the electrons tend tofollow a trochoidal path. It has been found in actual experiments thatthe efficiency of the unit is greatly increased when such an additionalelectrode is employed.

While I have shown the additional electrode 170 in coniiction with athermionic converter of the type shown in FIGURES 9 and 10, it is to beunderstood that a similar type of electrode could be employed inconnection with the other species. In each case, the contour of theadditional electrode would be selected to conform with an equi-potentialsurface existing at the area in which it is located.

It is also to be understood that in connection with any of theembodiments of my invention that a suitable grid can be employed betweenthe cathode and the anode to vary the emission from the cathode andhence to vary the output current.

While I have referred in numerous cases to electrodes being cylindricalin the specification and claims, it is to be understood that the termcylinder is to be construed in its broad geometric sense as the surfaceformed by any line being continuously moved parallel to a fixed line. Inother words, the term cylindrical as used in the specification andclaims is not intended to be limited to a right circular cylinder.

CONCLUSION It will be seen that I have provided a thermionic converterin which a magnetic field is employed to hold the electrons undercompression until they are forced out of the compression chamber atareas of irregularities or openings in the electrostatic orelectromagnetic field. At such irregularities, space charge waves aregenerated and the charged particles leave the compression. chamber withgreater individual kinetic energy than the average kinetic energy of thecharges within the compression chamber. Because of this additionalenergy, the charged particles can be collected on a high-1y chargedcollector electrode with great efficiency. The magnetic fields generatedby the rotating electrons are an additional aid in generating velocitytowards the collectors. Since the energy exchanges between the heatinput, the charged particles in the=cross-field space, and the collectorare extremely complex, no effort has been made to explain theseexchanges, except to point out the various actions known or suspected tooccur. For purposes of brevity, it should be sufficient to note that thecombination of a cathode to which heat is added, with a magnetron-likecompression chamber, and a concave or hollow collector enables an outputvoltage much higher than the one or two-volt limits of conventionalthermionic converters. By reason of the employment of a concavecollector surface, the presence of a virtual cathode in front of thecollector surface is materially reduced. It will also be seen that myarrangement is broad enough to contemplate either forcing' the electronsor other charged particles out of the end of the chamber 'into or ontocollectors disposed at the ends thereof or to cause the chargedparticles to pass out sidewise beyond the anode to engage an adjacentconcave collector surface.

While I have shown a number of embodiments of my invention, it is to beunderstood that this is for purposes of "illustration only and that thescope of the invention is to be limited solely by the appended claims.

I claim as my invention:

1. A thermionic converter for converting heat energy to electricalenergy comprising:

an enclosure including a cylindrical thermionic electron emissivecathode designed to emit electrons from the exterior cylindrical surfacethereof when said cathode is heated, means for accelerating saidelectrons comprising a. an anode having an elongated curved surfacespaced from and at least partially surrounding said cathode, andcollector having a concave conductive surface within said enclosure anddisposed so that said conductive surface extends beyond one extremity ofsaid anode so as to be in the path of electrons emitted by said cathodeand moving past said curved surface of said anode, a source of heat forapplying heat to said cathode, said source of heat being of a magnitudesuch that it constitutes the primary source of external energy appliedto said converter,

means for applying a positive voltage between said anode and cathode toaccelerate the passage of electrons from said cathode to said collector,

magnetic means surrounding said anode and producing a magnetic fieldgenerally parallel to the longitudinal axis of the curved surface ofsaid anode for confin- .ing the electrons emitted by said cathode andminimizing the tendency of said electrons to enage said anode,

and means operative to withdraw the electrical energy from saidconverter resulting from the heat applied to said cathode,

said means including a utilization circuit connected between saidcollector and said cathode to withdraw the energy from said collectordue to the electrons engaging the conductive surface thereof, saidutilization circuit being free of any external electrical source ofpower of the same order of magnitude of energy as that of said source ofheat.

2. The converter of claim 1 in which the anode is a cylindrical membercompletely surrounding said cathode and in which the collector isadjacent one end of said anode.

3. The converter of claim 1 in which the anode extends only partiallyaround the cathode and in which the collector surrounds the cathode overa sector through which the anode does not extend.

4. The converter of claim 2 in which the collector is hollow and has anopening facing the region between said cathode and anode.

5. The converter of claim 2 in which the magnetic field diverges in thedirection of the collector.

6. The converter of claim 2 in which there is an additional collectordisposed intermediate the opposite ends of said anode.

7. The converter of claim 6 in which the additional collector is in theform of a he-lically wound coil.

8. The converter of claim 6 in which the additional collector is in theform of a flat plate.

9. The converter of claim 2 in which the collector consists of twoportions each disposed adjacent an opposite end of said anode.

10. The converter of claim 9 in which the two portions of said collectorare each hollow and each has an opening facing the region between saidcathode and anode.

11. The converter of claim 1 in which the cathode is tubular and inwhich the source of heat is a source of heated fluid which is circulatedthrough said cylindrical cathode.

12. The converter of claim 1 in which the cathode includes radioactivematerial which constitutes the source of heat.

13. The converter of claim 1 in which the collector is of magneticmaterial.

14. The converter of claim 1 in which the collector is hollow and one ormore pick-up probes or field forming electrodes are placed within, orform the end of the collector.

15. The converter of claim 1 in which the source of heat is a reflectoradapted to be exposed to solar energy and in which the cathode isadjacent to the focal point of the reflector.

16. The converter of claim 1 in which axial barlike electrodes extendaxially inside of said anode and are maintained at a different potentialthan said anode.

17. The converter of claim 1 in which there is an additional electrodedisposed beyond one extremity of the anode and which is maintained at apotential such as to maximize the amount of energy withdrawn from saidconverter.

18. The converter of claim 1 in which there is a coupling betweenelectrodes of the converter to cause oscillations which aid electronflow to the collector.

19. The converter of claim 1 in which there is a grid for controllingelectron flow from the cathode.

20. A thermionic converter for converting heat energy to electricalenergy comprising:

an enclosure including a cylindrical thermionic electron emissivecathode designed to emit electrons from the exterior cylindrical surfacethereof when said cathode is heated,

means for accelerating said electrons comprising an anode having anelongated curved surface spaced from and at least partially surroundingsaid cathode, and

a collector having a conductive surface within said enclosure andextending across the corresponding axial ends of said cathode and saidaccelerating means so that said conductive surface lies across the pathof electrons emitted by said cathode and moving past the end of saidcurved surface of said anode,

a source of heat for applying heat to said cathode, said source of heatbeing of a magnitude such that it constitutes the primary source ofexternal energy applied to said converter,

means for applying a positive voltage between said anode and cathode toaccelerate the passage of electrons from said cathode to said collector,

magnetic means surrounding said anode and producing a magnetic fieldgenerally parallel to the longitudinal axis of the curved surface ofsaid anode for confining the electrons emitted by said cathode andminimizing the tendency of said electrons to engage said anode,

and means operative to withdraw the electrical energy from saidconverter resulting from the heat applied to said cathode,

said means including a utilization circuit connected between saidcollector and said cathode to withdraw the energy from said collectordue to the electrons engaging the conductive surface thereof, saidutiliza- 1 6 tion circuit being free of any external electrical sourceof power of the same order of magnitude of energy as that of said sourceof heat. z 21. A thermionic converter for converting heat energy toelectrical energy comprising:

an enclosure including v a cylindrical source of charged particlesdesigned to cause charged particles to move from the exteriorcylindrical surface thereof when said electrode is heated,

means for accelerating said charged particles comprising a secondcylindrical electrode surrounding said first named electrode, and

a collector having a conductive surface within said enclosure andextending adjacent one end of said second electrode,

a source of heat for introducing heat within the interior of said firstnamed hollow electrode, said source of heat being of a magnitude suchthat it constitutes the primary source of external energy applied tosaid converter,

means for applying a voltage between said second electrode and saidfirst named electrode to accelerate the passage of charged particlesfrom said first named electrode to said collector,

magnetic means surrounding said second electrode and producing amagnetic field generally parallel to the axis of said second electrodefor confining the charged particles moving from said first electrode andminimizing the tendency of said charged particles to engage said secondnamed electrode, and means operative to withdraw the electrical energyfrom said converter resulting from the heat applied to said cathode,

said means including a utilization circuit connected between saidcollector and said first named electrode to Withdraw the energy fromsaid collector due to the charged particles engaging the conductivesurface thereof, said utilization circuit being free of any externalelectrical source of power of the same order of magnitude of energy a asthat of said source of heat.

References Cited UNITED STATES PATENTS 8/1966 Fox 310-4 9/1966 Laing eta1. 322-2 U.S. Cl. X.R.

